JP2009174426A - Exhaust emission control device and temperature control method for exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device and a temperature control method for the exhaust emission control device, raising the temperature of the exhaust emission control device such as a NOx cleaning catalyst and a DPF in a short time, maintaining the temperature thereof in a range of high cleaning performance, and improving a cleaning function. <P>SOLUTION: This exhaust emission control device 3 cleaning exhaust gas G from an internal combustion engine is provided with: a hollow portion 4 formed in a part of or the whole of the surface or inside of the exhaust emission control device 3 and circulating fluid A; fluid flow rate regulating mechanisms 5, 5a, 6, 6a, 7, 11 regulating a flow rate of fluid A in the hollow portion 4; and fluid pressure regulating mechanisms 5a, 6a, 7, 11 sealing the hollow portion 4 to regulate pressure of the fluid A in the hollow portion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides an exhaust gas that can be quickly heated when exhaust gas purification is performed by an exhaust gas purification device such as a NOx occlusion reduction catalyst or a DPF, and that the temperature can be easily maintained within a temperature range with high purification performance. The present invention relates to a temperature control method for a purification device and an exhaust gas purification device.

  There is a NOx purification catalyst for purifying NOx (nitrogen oxide) in exhaust gas. In one of these NOx purification catalysts, an alkali metal or alkaline earth metal is supported together with a noble metal, and NO (nitrogen monoxide) in exhaust gas containing excess oxygen is oxidized and adsorbed on the catalyst as nitrate. There is a NOx occlusion reduction type catalyst for purifying gas. This NOx occlusion reduction type catalyst occludes NOx when the exhaust gas is in a lean air-fuel ratio state where the oxygen concentration is high, and releases the occluded NOx and releases it in a rich air-fuel ratio state where the oxygen concentration is low or zero. NOx is reduced in a reducing atmosphere to reduce NOx.

In the NOx purification device provided with this NOx occlusion reduction type catalyst, as shown in FIG. 5, the NOx purification function depends on the catalyst temperature. The effect of the catalyst temperature on the NOx purification performance is great, and the purification performance can be exerted at a temperature higher than 200 ° C., and the purification performance becomes the highest in the temperature range of 300 ° C. to 400 ° C. In addition, as the catalyst temperature increases, the ratio of NO ₂ (nitrogen dioxide) in NOx decreases, and the ratio of NO that hardly changes to nitrate increases. Therefore, the catalyst temperature exceeds 400 ° C. Then, the NOx purification rate is reduced. Therefore, when exhaust gas purification is performed by the exhaust gas purification device of the NOx occlusion reduction type catalyst, the catalyst temperature should be kept in the temperature range R of about 250 ° C. to 400 ° C. in that the catalyst performance is fully exhibited. Is preferred. In addition, in other NOx purification catalysts, oxidation catalysts, and the like, the temperature range in which proper purification ability can be exhibited is often limited.

  However, in an internal combustion engine mounted on an automobile used for multiple purposes, a NOx occlusion reduction type catalyst that has a limited temperature range that can purify NOx despite the wide exhaust gas temperature range is used. Has a problem that NOx can be sufficiently purified only in a limited temperature range.

  For example, after the engine is started, the exhaust gas temperature is low, and the catalyst temperature is kept at a low temperature of 250 ° C. or lower. Thereafter, as the engine output increases, the exhaust gas temperature increases, but the NOx concentration inevitably increases. However, when ceramics with many pores are used for the catalyst carrier, the catalyst temperature rises slower than the NOx concentration and exhaust gas temperature rise. Therefore, until the catalyst temperature is in a temperature range where the purification capability of the catalyst can be sufficiently exhibited, the purification capability is not sufficiently exhibited, and relatively high concentration of NOx is discharged into the atmosphere. Further, when the engine output continues to be high, the exhaust gas temperature continues to be high, so the catalyst temperature also becomes high. Therefore, when the catalyst temperature exceeds 400 ° C., the NOx purification rate decreases, and a relatively high concentration of NOx is discharged into the atmosphere.

  Also, in an exhaust gas purification device equipped with a DPF (diesel particulate filter) that collects PM (particulate matter) in the exhaust gas, the temperature of the DPF rises quickly above the combustion temperature of the PM during regeneration. Thus, it is necessary to burn the PM and maintain the temperature of the DPF within a predetermined temperature range so that the DPF is not damaged at a high temperature.

  Therefore, in an exhaust gas purification device equipped with a catalyst such as a NOx storage reduction catalyst or a DPF mounted on a vehicle, it is important to raise the temperature of the exhaust gas purification device to a predetermined temperature range in a short time depending on operating conditions. In addition, it is important to maintain the temperature of the exhaust gas purification device within a predetermined temperature range under high-load engine operating conditions where the exhaust gas temperature becomes high.

  Regarding the temperature control of this exhaust gas purification device, it is a NOx purification catalyst of the selective catalytic reduction method, but a porous exhaust gas purification material is installed in the middle of the exhaust gas flow path, and this exhaust gas purification material and this exhaust gas purification catalyst are installed. Cooling means consisting of a dual structure exhaust gas conduit consisting of an outer layer and an inner pipe and a refrigerant circulation device is provided in the exhaust gas conduit on the upstream side of the material to circulate the refrigerant in either the outer layer or the inner pipe, There has been proposed an exhaust gas purification device that lowers the surface temperature of an exhaust gas purification material by blowing air on the surface of the purification material (see, for example, Patent Document 1).

  In this exhaust gas purification device, cooling water or the like is used as the refrigerant, the heat of the refrigerant is dissipated by a radiator, air is introduced into the exhaust gas, or a variable area heat dissipating material is provided on the outer surface of the exhaust gas conduit. Then, the temperature of the exhaust gas purification device is lowered, while the temperature of the exhaust gas purification device is raised by heating with a heater or a reduction in the flow rate of the exhaust gas.

  Further, at least one of the exhaust gas treatment device of the engine such as DPF or NOx reduction catalyst and the upstream exhaust passage is made into a double structure, and the replacement gas is replaced with the air and the replacement gas in the double structure. In this case, an exhaust gas treatment apparatus that evacuates the double structure and a heat insulation structure of the exhaust passage have been proposed (for example, see Patent Document 2).

  In this heat insulation structure, the convection heat transfer is reduced by the vacuum of the double structure, and the radiation heat transfer (radiation heat transfer) is reduced by the radiation heat shield plate, so that the apparatus has excellent heat retention. By improving the heat retention, the reduction of the exhaust gas temperature due to heat dissipation is reduced, and the deterioration of the fuel consumption when the exhaust gas temperature rises for filter regeneration is suppressed.

However, the former exhaust gas purification device is suitable for lowering the temperature because it mainly dissipates heat, but there is a problem that the temperature rise is insufficient, and the latter exhaust gas treatment device and the heat insulation structure of the exhaust passage are mainly for heat insulation. Therefore, there is a problem that it is suitable for raising the temperature but not suitable for lowering the temperature.
JP 07-284636 A JP 2002-349259 A

  The present invention has been made in view of the above-described situation, and an object of the present invention is to increase the temperature of an exhaust gas purification device such as a NOx purification catalyst and a DPF in a short time, and to achieve purification performance. An object of the present invention is to provide an exhaust gas purification device and a temperature management method for the exhaust gas purification device that can be maintained within a high temperature range and can improve the purification function.

  An exhaust gas purifying apparatus for achieving the above object is an exhaust gas purifying apparatus for purifying exhaust gas of an internal combustion engine, wherein fluid flows through a part or all of the surface or inside of the exhaust gas purifying apparatus. And a fluid flow rate adjusting mechanism for adjusting the flow rate of the fluid in the hollow portion, and a fluid pressure adjusting mechanism for adjusting the pressure of the internal fluid by sealing the hollow portion. . The fluid flow rate adjusting mechanism and the fluid pressure adjusting mechanism may be used as a whole mechanism, a part of the mechanisms in common use, or a completely different mechanism.

  As a configuration having both functions of adjusting the flow rate of the fluid and adjusting the pressure of the fluid, that is, a configuration capable of introducing and discharging the fluid, for example, an electromagnetic valve provided on the fluid inlet side of the hollow portion, and a fluid There is a combination of a solenoid valve provided on the outlet side and a vacuum pump provided on the downstream side of the solenoid valve on the fluid outlet side, and by opening both solenoid valves and operating the vacuum pump, the fluid flow rate can be reduced. Can be adjusted. Also, by closing the solenoid valve on the fluid inlet side, opening the solenoid valve on the fluid outlet side and operating the vacuum pump, the pressure of the fluid can be reduced to a vacuum, and a predetermined degree of vacuum has been reached. Sometimes, by closing the solenoid valve on the fluid outlet side and stopping the vacuum pump, the hollow portion can be maintained at a predetermined vacuum level.

  According to the configuration of this exhaust gas purification device, a fluid such as a gas or a liquid is allowed to flow through the hollow portion of a container such as a NOx purification catalyst or a DPF, thereby efficiently exchanging heat between the fluid and the NOx purification catalyst or the DPF. In addition, the temperature of the fluid in the hollow portion can be reduced, or the fluid can be removed and the vacuum can be established to efficiently maintain the temperature.

  In the exhaust gas purification system, when the fluid flow rate adjustment mechanism is configured to have a fluid switching mechanism that switches the fluid flowing through the hollow portion between the exhaust gas and the air, the configuration allows the hollow portion to be heated with the high-temperature exhaust gas. Thus, the exhaust gas purification device can be warmed through the air and the heat retention effect can be increased, and the exhaust gas purification device can be cooled through the hollow portion with low-temperature air.

  In the above exhaust gas purification system, when at least one of the fluid flow rate and the fluid pressure in the hollow portion is adjusted according to the operating state of the internal combustion engine, the exhaust gas discharged from the internal combustion engine can be obtained by this configuration. It is possible to perform adjustment control of the heat radiation amount and the heat reception amount corresponding to the temperature of the exhaust gas, and it becomes possible to more appropriately manage the temperature of the exhaust gas purification device.

  And the temperature management method of the exhaust gas purification apparatus for achieving the above object is the temperature management method of the exhaust gas purification apparatus for purifying the exhaust gas of the internal combustion engine. The fluid of the exhaust gas purifier is adjusted by adjusting the flow rate of the fluid and adjusting the pressure of the fluid when the hollow portion is sealed, while allowing the fluid to flow through the hollow portion provided in part or in whole. It is a temperature management method characterized by adjusting the entrance and exit.

  According to this method, a fluid can be passed through the hollow portion of the container of the exhaust gas purification apparatus such as the NOx purification catalyst and the DPF, and heat can be exchanged between the fluid and the NOx purification catalyst and the DPF. It is possible to keep the temperature in a vacuum state by reducing the pressure of the fluid in the section or removing the fluid.

  In the temperature management method of the exhaust gas purification device described above, when the fluid to be circulated in the hollow portion is switched to exhaust gas and air, the exhaust gas purification device is warmed through the hollow portion with high-temperature exhaust gas by this method, The heat retention effect can be increased, and the exhaust gas purification device can be cooled through the hollow portion with low-temperature air.

  In the temperature management method of the exhaust gas purifying apparatus described above, when at least one of the fluid flow rate and the fluid pressure in the hollow portion is adjusted according to the operating state of the internal combustion engine, the exhaust gas discharged from the internal combustion engine by this method The amount of heat radiation and the amount of heat received corresponding to the temperature can be adjusted, and the temperature management of the exhaust gas purification device can be performed more appropriately.

  In the temperature management method for an exhaust gas purifying apparatus described above, when the temperature of the exhaust gas purifying apparatus is low, the hollow portion is evacuated and transmitted through the hollow portion until reaching a predetermined temperature range. When the amount of heat to be heated is reduced and the temperature of the exhaust gas purifying device is within the predetermined temperature range, or when predicted to be within the predetermined temperature range, the hollow portion is maintained in a vacuum state, Further, when the temperature of the exhaust gas purification device exceeds the predetermined temperature range, or when the temperature of the exhaust gas purification device is predicted to exceed the predetermined temperature range, the fluid is circulated through the hollow portion. Let

  According to this control, when the temperature of the exhaust gas purifying device is low, it is possible to reduce the time required to reach a predetermined temperature range by making the hollow portion in a vacuum state and reducing the heat radiation amount. Also, when the temperature of the exhaust gas purification device is within a predetermined temperature range, or when the temperature of the exhaust gas purification device is predicted to be within the predetermined temperature range, the hollow portion is maintained in a vacuum state. Thus, the temperature of the exhaust gas purification device can be maintained within a predetermined temperature range. Furthermore, when the temperature of the exhaust gas purification device exceeds a predetermined temperature range, or when the temperature of the exhaust gas purification device is predicted to exceed the predetermined temperature range, by convection heat transfer of the hollow portion, Heat can be taken from the exhaust gas purification device to cool the exhaust gas purification device. The degree of cooling can be adjusted by adjusting the flow rate of the fluid in the hollow portion, which greatly affects the amount of convection heat transfer, by adjusting the flow rate of the fluid. Therefore, the temperature of the exhaust gas purification device such as the NOx purification catalyst and the DPF can be easily raised, adjusted and managed.

  According to the exhaust gas purification device and the temperature management method of the exhaust gas purification device according to the present invention, the amount of heat radiated from the exhaust gas purification device can be adjusted by the flow rate of the fluid flowing through the hollow portion, and Since the heat radiation amount can be significantly reduced by the pressure drop state, in other words, by the vacuum state, the temperature management of the exhaust gas purifying device can be easily performed by the function of adjusting the heat radiation amount.

  Therefore, the temperature of the exhaust gas purification device can be efficiently raised within a temperature range with high purification performance in a short time, and can easily be maintained within the temperature range with high purification performance. The purification function of the purification device can be improved. Moreover, since the volume of the exhaust gas purification device required for purification can be reduced by improving the purification capability, the size can be reduced, and the mountability on the vehicle can also be improved by the reduction in size.

  Hereinafter, an exhaust gas purification system and an exhaust gas purification method according to embodiments of the present invention will be described with reference to the drawings. In addition, although gas is demonstrated as a fluid here, liquids, such as cooling water, can also be used as a fluid. In addition, the “vacuum” and “vacuum state” used here do not need to be absolute atmospheric pressure zero, but may be lower than atmospheric pressure and have a heat insulating effect in the hollow portion. This vacuum state can be easily implemented by sealing the hollow portion and sucking it with a vacuum pump (vacuum pump). The degree of vacuum is determined by the structural strength of the hollow part and the performance of the sealing valve or vacuum pump, but these are determined by the balance between the heat insulation requirement and the effect in the hollow part.

  FIG. 1 shows a configuration of an exhaust gas purification system 1 using an exhaust gas purification device according to an embodiment of the present invention, and FIG. 2 shows a cross-sectional view of the exhaust gas purification device. The exhaust gas purification system 1 is formed in an engine exhaust passage 2 by one or several combinations of an oxidation catalyst (DOC), a NOx storage reduction catalyst (LNT), a diesel particulate filter (DPF), and the like. An exhaust gas purification device 3 is arranged. Here, the exhaust gas purification device 3 will be described as including a NOx storage reduction catalyst.

  This NOx occlusion reduction type catalyst is formed by supporting an alkali metal or alkaline earth metal together with a noble metal, and purifies NOx by oxidizing NO in exhaust gas containing excess oxygen and adsorbing it as a nitrate on the catalyst. The NOx occlusion reduction type catalyst occludes NOx when the exhaust gas is in a lean air-fuel ratio with a high oxygen concentration, and releases the occluded NOx and releases it in a rich air-fuel ratio with a low or zero oxygen concentration. NOx is reduced in a reducing atmosphere to reduce NOx.

  A hollow portion 4 through which a fluid (here, gas) A of exhaust gas G or air (outside air) B flows is provided on a part or the whole of the surface of the exhaust gas purification device 3. The hollow portion 4 is normally provided in the outer peripheral portion of the exhaust gas purification device 3, but may be provided in the interior when the exhaust gas purification device 3 has an internal passage. If this hollow portion is provided on the inlet side of the exhaust gas G of the exhaust gas purification device 3, it can exert a temperature management effect on the exhaust gas G, and if it is provided on the outlet side of the exhaust gas G, the rear portion of the exhaust gas purification device 3 The temperature control effect on the edge can be demonstrated. If this hollow portion 4 is also provided in the exhaust passage 2 on the upstream side of the exhaust gas purification device 3, the temperature management effect on the exhaust gas G flowing into the exhaust gas purification device 3 can be further increased.

  In this hollow portion 4, an inlet side pipe 5 as a fluid A supply part and an outlet side pipe 6 as a fluid A discharge part are connected, and an inlet side electromagnetic valve 5 a is provided in the inlet side pipe 5. The outlet side solenoid valve 6 a is provided in the outlet side pipe 6. Further, a vacuum pump 7 is provided on the downstream side of the outlet side solenoid valve 6a. Further, the inlet side pipe 5 is provided on the downstream side with respect to the exhaust gas G of the exhaust gas purification device 3, and the outlet side pipe 6 is provided on the upstream side. Thus, a fluid flow rate adjusting mechanism for adjusting the flow rate of the fluid A in the hollow portion 4 and a fluid pressure adjusting mechanism for sealing the hollow portion 4 and adjusting the pressure of the fluid A inside are configured.

  The upstream side of the inlet side pipe 5 is configured so that the exhaust gas G and the air B can be selected and introduced. That is, the upstream side of the inlet side pipe 5 is branched into two, one inlet side pipe 5b is opened to the atmosphere, and the other inlet side pipe 5c is connected to the exhaust passage 2 on the downstream side of the exhaust gas purification device 3. Connecting. At the same time, a switching valve 8 is provided at this branch portion. With this configuration, the fluid flow rate adjustment mechanism has a fluid switching mechanism that switches the fluid A flowing through the hollow portion 4 to the exhaust gas G and the air B. With this configuration, the exhaust gas purifying device 3 can be efficiently warmed with the high-temperature exhaust gas G through the hollow portion 4, and the heat retention effect can be increased. The exhaust gas purification device 3 can be efficiently cooled.

  Further, a temperature sensor 9 for measuring the temperature Tm of the exhaust gas purification device 3 is provided inside the exhaust gas purification device 3. When it is difficult to provide the temperature sensor 9 inside, a temperature sensor 9a for measuring the temperature Tg of the exhaust gas G is provided on the upstream side of the exhaust gas purification device 3, and the detected temperature Tga of this temperature sensor is set as the temperature. Substitute for Tm. Furthermore, a pressure sensor 10 for measuring the pressure Pm of the hollow portion 4 is provided. Further, if necessary, a temperature sensor 9b that measures the temperature Tgb of the exhaust gas G is provided on the downstream side of the exhaust gas purification device 3, and is used to determine whether the exhaust gas G can be warmed up. .

  The detected values Tm (Tga) and Tgb of the temperature sensors 9 (9a) and 9b and the detected value Pm of the pressure sensor 10 are input to the control device 11 of the exhaust gas purification device 3. The control device 11 also receives an engine speed Ne and a load (or fuel injection amount) Q that indicate the operating state of the engine, and controls the inlet side solenoid valve 5a, the outlet side solenoid valve 6a, the vacuum pump 7, and the switching valve 8. Control. Normally, the control device 11 is built in an engine control device 20 called an ECM (engine control module) or ECU (engine control unit) that controls the operation of the engine.

  If both the solenoid valves 5a and 6a are opened and the vacuum pump 7 is operated, the flow rate of the fluid A can be adjusted by adjusting the vacuum pump 7, and the solenoid valve 5a on the fluid inlet side is closed and the fluid outlet side is closed. When the electromagnetic valve 6a is opened and the vacuum pump 7 is operated, the pressure of the fluid A can be reduced to make a vacuum, and when the predetermined vacuum degree is reached, the vacuum pump 7 is stopped. This vacuum state is always detected by the pressure sensor 10, and the vacuum pump 7 is operated again when the vacuum level rises above a predetermined degree of vacuum (predetermined pressure). In other words, the vacuum pump 7 is stopped until the pressure sensor 10 detects that the pressure is equal to or lower than the predetermined pressure value. Thereby, the hollow part 4 can be maintained with a vacuum state. These controls are performed according to the operating state of the engine.

  Next, the temperature management method for the exhaust gas purifying apparatus will be described with reference to the control flow of FIG. 3 for the first embodiment. The control flow of FIG. 3 is shown as starting with the start of engine operation, being executed in parallel with the engine operation control, and returning and ending with the end of engine operation.

  When the control flow of FIG. 3 starts, it is determined in step S11 whether the catalyst temperature Tm is lower than a lower limit (for example, 250 ° C.) Tc1 of a predetermined temperature range (YES) or not (NO). If the determination in step S11 is low (YES), go to step S12. In step S12, prior to evacuation, it is determined whether the pressure Pm of the hollow portion 4 is lower than a predetermined pressure Pc (YES) or not (NO). If it is low (YES), it is determined that the vacuum has already been reached, and the process returns to step S11. When it is not low (NO), the process goes to step S13 to evacuate. This evacuation is performed for a predetermined time (time related to the pressure Pm determination interval) by closing the inlet side electromagnetic valve 5a, opening the outlet side electromagnetic valve 6a, and operating the vacuum pump 7.

  After this evacuation, in step S14, it is determined again whether the pressure Pm of the hollow portion 4 is lower than the predetermined pressure Pc (YES) or not (NO). When it is low (YES), the process goes to Step S15, the operation of the vacuum pump 7 is stopped, the evacuation is stopped, and the process returns to Step S11. If not (NO), the process returns to step S13, and the evacuation in step S13 is continued until the pressure Pm of the hollow portion 4 becomes lower than the predetermined pressure Pc. By evacuating the hollow portion 4, the heat insulating effect of the hollow portion 4 is enhanced, and the temperature of the exhaust gas purification device 3 can be efficiently increased.

  If it is determined in step S11 that the catalyst temperature Tm is not lower than the lower limit Tc1 of the predetermined temperature range (NO), the catalyst temperature Tm is higher than the upper limit (eg, 400 ° C.) Tc2 of the predetermined temperature range in step S16. (YES) or not (NO). When it is not high (NO), the process goes to step S12, and the hollow portion 4 is evacuated or maintained in a vacuum state. When it is high (YES), the process goes to step S17, and the fluid A is circulated through the hollow portion 4. This circulation is performed for a predetermined time (time related to the determination interval of the catalyst temperature) by opening both the inlet side electromagnetic valve 5a and the outlet side electromagnetic valve 6a and operating the vacuum pump 7. Here, since it is for cooling, the switching valve 8 is switched and the air B is distribute | circulated.

  Further, when the operation of the engine is finished, an interrupt is generated even during the control, and the routine returns, and this control flow is finished together with the end of the operation of the engine.

  According to the temperature management method for the exhaust gas purifying device of the first embodiment, when the temperature Tm of the exhaust gas purifying device 3 is low, the hollow portion is reached until it reaches a predetermined temperature range (Tc1 to Tc2). If the temperature Tm of the exhaust gas purification device is within a predetermined temperature range (Tc1 to Tc2), the amount of heat heated through the hollow portion 4 is reduced by making the vacuum state 4 and the hollow portion 4 is in a vacuum state. If the temperature Tm of the exhaust gas purification device 3 exceeds a predetermined temperature range (Tc1 to Tc2), the fluid A (air B) is circulated through the hollow portion 4.

  Although the control determination is performed at the temperature Tm, the lower limit Tc1 and the upper limit Tc2 of the predetermined temperature range, the change of the temperature Tm can be predicted by making the determination taking into account the increase / decrease speed of the temperature Tm. Can be easily expanded even when the temperature is predicted to fall within a predetermined temperature range or when the temperature Tm is predicted to exceed the predetermined temperature range. Further, if the exhaust gas temperature is predicted based on the engine speed Ne and the fuel injection amount Q, which are closely related to the temperature Tga of the exhaust gas G exhausted from the engine, or the engine speed Ne and the fuel injection If the quantity Q is used as a criterion for determination, it is possible to control heat dissipation and heat retention from the exhaust gas purification device 3 before the exhaust gas temperature Tga changes, and to reduce the time delay of these controls. it can.

  Therefore, according to this temperature management method, when the temperature Tm of the exhaust gas purifying device 3 is low, the hollow portion 4 is evacuated to reduce the heat radiation amount and reach a predetermined temperature range (Tc1 to Tc2). The time until can be reduced. Further, when the temperature Tm of the exhaust gas purification device 3 is within the predetermined temperature range (Tc1 to Tc2) or when it is predicted to be within the predetermined temperature range (Tc1 to Tc2), the hollow portion 4 is kept in the vacuum state. The temperature Tm of the exhaust gas purification device 3 can be maintained within a predetermined temperature range (Tc1 to Tc2). Further, when the temperature Tm of the exhaust gas purification device 3 exceeds or is predicted to exceed a predetermined temperature range (Tc1 to Tc2), heat is generated from the exhaust gas purification device 3 by convection heat transfer or the like of the hollow portion 4. The exhaust gas purification device 3 can be cooled. This degree of cooling can be adjusted by adjusting the flow rate of the fluid A. Therefore, the temperature Tm of the exhaust gas purification device 3 such as a NOx purification catalyst or DPF can be easily adjusted and managed.

  Next, a temperature management method for the exhaust gas purifying apparatus according to the second embodiment will be described with reference to the control flow of FIG. The control flow of FIG. 4 is obtained by adding steps S21 and S22 to the control flow of FIG.

  In the control flow of FIG. 4, when the catalyst temperature Tm is lower than the lower limit Tc1 of the predetermined temperature range in step S11, the temperature Tgb of the exhaust gas G on the downstream side of the exhaust gas purification device 3 is the predetermined determination temperature in step S21. It is determined whether it is higher than Tc3 (YES) or not (NO), and only when it is higher (YES), the process goes to step S22 to circulate the exhaust gas G having a relatively high temperature through the hollow portion 4 to purify the exhaust gas. The device 3 is warmed.

  This distribution is performed by opening both the inlet side solenoid valve 5a and the outlet side solenoid valve 6a and operating the vacuum pump 7. Here, because of warming up, the switching valve 8 is switched to exhaust gas. G is distributed. By adjusting the flow rate and flow velocity of the exhaust gas G by adjusting the vacuum pump 7, the degree of warm-up can be adjusted.

  The predetermined determination temperature Tc3 is a temperature at which the exhaust gas purification device 3 can be efficiently warmed. As the predetermined determination temperature Tc3, a value that varies depending on the catalyst temperature Tm (for example, a value obtained by adding a constant temperature to the catalyst temperature Tm) may be used.

  If it is determined at step S21 that the temperature Tgb of the exhaust gas G is not higher than the predetermined determination temperature Tc3 (NO), the process goes to step S12. Otherwise, the same control as in the control flow of FIG. 3 is performed.

  According to the temperature management method of the second embodiment, in addition to the operational effects of the temperature management method of the first embodiment, when the catalyst temperature Tm is lower than the lower limit Tc1 of the predetermined temperature range, the exhaust gas When the temperature Tab of G is high, the exhaust gas G can be circulated through the hollow portion 4 to warm up.

  According to the exhaust gas purification device and the temperature management method of the exhaust gas purification device, the amount of heat radiated from the exhaust gas purification device 3 can be adjusted by the flow rate of the fluid A flowing through the hollow portion 4, and Since the heat radiation amount can be remarkably reduced by the pressure drop state of the fluid A, in other words, in the vacuum state, the temperature management of the exhaust gas purification device 3 can be easily performed by this heat radiation amount adjustment function.

  Therefore, the temperature Tm of the exhaust gas purification device 3 can be efficiently raised within a temperature range (Tc1 to Tc2) with high purification performance in a short time, and within the temperature range (Tc1 to Tc2) with high purification performance. Therefore, the purification function of the exhaust gas purification device 3 can be improved.

  As a result, when the catalyst temperature Tm is lower than the temperature range (Tc1 to Tc2) required for the catalyst function, the time delay of the catalyst temperature Tm with respect to the rise of the exhaust gas temperature Tga can be reduced, so the amount of NOx emitted from the engine Can be further suppressed. Further, when the catalyst temperature Tm is higher than the temperature range (Tc1 to Tc2) necessary for the catalyst function to be expressed, it is possible to suppress the NOx emission from the engine by increasing the heat release from the catalyst and promoting the cooling. Become.

  Furthermore, if heat dissipation and heat insulation control are handled prior to the change in engine exhaust gas temperature, the control time delay can be reduced, and further, the purification efficiency of the catalyst is improved, so that NOx emissions are further suppressed. Is possible.

It is a figure which shows the structure of the exhaust-gas purification system using the exhaust-gas purification apparatus of embodiment of this invention. 1 is a cross-sectional view of an exhaust gas purification device according to an embodiment of the present invention. It is a figure which shows an example of the control flow of the temperature management method of the exhaust-gas purification apparatus of the 1st Embodiment of this invention. It is a figure which shows an example of the control flow of the temperature management method of the exhaust-gas purification apparatus of the 2nd Embodiment of this invention. It is a figure which shows the relationship between the catalyst temperature of NOx storage reduction type catalyst, and purification performance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification system 2 Engine exhaust passage 3 Exhaust gas purification apparatus 4 Hollow part 5 Inlet side piping 5a Inlet side solenoid valve 5b One inlet side piping 5c The other inlet side piping 6a Outlet side solenoid valve 6 Outlet side piping 7 Vacuum Pump 8 Switching valve 9, 9a, 9b Temperature sensor 10 Pressure sensor 11 Controller 20 Engine controller A Fluid B Air (atmosphere)
G Exhaust gas Ne Engine speed Q Load (or fuel injection amount)
Tc1 Lower limit of the predetermined temperature range Tc2 Upper limit of the predetermined temperature range Tc3 Predetermined determination temperature Tga Temperature of the exhaust gas upstream of the exhaust gas purification device Tgb Temperature of the exhaust gas downstream of the exhaust gas purification device Tm Exhaust gas purification device Temperature (catalyst temperature)

Claims (7)

  In an exhaust gas purification device for purifying exhaust gas of an internal combustion engine, a hollow portion through which a fluid flows is provided on a part or all of the surface or inside of the exhaust gas purification device, and the flow rate of the fluid in the hollow portion is adjusted. An exhaust gas purifying apparatus characterized in that a fluid flow rate adjusting mechanism is provided and a fluid pressure adjusting mechanism is provided for adjusting the pressure of the internal fluid by sealing the hollow portion.   The exhaust gas purifying apparatus according to claim 1, wherein the fluid flow rate adjusting mechanism includes a fluid switching mechanism that switches a fluid flowing through the hollow portion between exhaust gas and air.   The exhaust gas purification device according to claim 1 or 2, wherein at least one of a fluid flow rate and a fluid pressure in the hollow portion is adjusted according to an operating state of the internal combustion engine.   In a temperature management method for an exhaust gas purification device for purifying exhaust gas of an internal combustion engine, a fluid is circulated through a hollow portion provided in a part or the whole of the surface or inside of the exhaust gas purification device, and the flow rate of the fluid And adjusting the pressure of the fluid when the hollow portion is sealed to adjust the heat input and output of the exhaust gas purification device.   The temperature management method for an exhaust gas purification device according to claim 4, wherein the fluid flowing through the hollow portion is switched between exhaust gas and air.   6. The temperature management method for an exhaust gas purification device according to claim 4, wherein at least one of a fluid flow rate and a fluid pressure in the hollow portion is adjusted according to an operating state of the internal combustion engine. When the temperature of the exhaust gas purifying device is low, the amount of heat transferred through the hollow portion is reduced in a vacuum state until the temperature reaches a predetermined temperature range,
When the temperature of the exhaust gas purifying device is within the predetermined temperature range, or when predicted to be within the predetermined temperature range, the hollow portion is maintained in a vacuum state,
Further, when the temperature of the exhaust gas purification device exceeds the predetermined temperature range, or when the temperature of the exhaust gas purification device is predicted to exceed the predetermined temperature range, the fluid is circulated through the hollow portion. The temperature management method for an exhaust gas purifying apparatus according to claim 4, wherein:

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